ppk1

PPK1, short for polyphosphate kinase 1, is a bacterial enzyme that catalyzes the synthesis of polyphosphate (polyP), a linear polymer of inorganic phosphate, by transferring phosphate units from ATP to an existing polyP chain. The typical overall reaction is (polyP)n + ATP → (polyP)n+1 + ADP. Through this activity, PPK1 serves as a major driver of polyP accumulation, especially under nutrient-limited conditions when cells store phosphate and energy for future use.

PPK1 is encoded by the ppk1 gene in many bacterial genomes and belongs to the polyphosphate kinase family. It is usually a cytosolic, soluble enzyme and is functionally distinct from the related PPK2 enzyme, which more often uses polyP to regenerate nucleotides. PPK1 activity is connected to cellular phosphate status and is often coordinated with phosphate-starvation responses in bacteria, such as the Pho regulon in several species. Beyond phosphate storage, polyP participates in stress tolerance, stationary-phase survival, biofilm formation, DNA protection, and, in some pathogens, virulence.

From a research and clinical perspective, PPK1 is of interest as a potential antimicrobial target because disrupting polyP synthesis can reduce bacterial virulence and stress resilience in certain pathogens. In biotechnological contexts, engineered PPK1 activity has been explored to increase polyP production for industrial applications and phosphate-recovery processes.

The study of PPK1 emerged from investigations into bacterial polyphosphate metabolism in the late 20th century, with subsequent structural and mechanistic analyses revealing conserved motifs essential for nucleotide binding and catalysis.